Problem: Solve for $r$, $ \dfrac{2r}{4r + 2} = \dfrac{1}{5} $
Solution: Multiply both sides of the equation by $4r + 2$ $ 2r = \dfrac{4r + 2}{5} $ Multiply both sides of the equation by $5$ $ 10r = 4r + 2 $ $6r = 2$ $r = \dfrac{2}{6}$ Simplify. $r = \dfrac{1}{3}$